Information technology has revolutionized the way in which data is exchanged in a computer network among various users. Computer networks deploy network devices such as routers, hubs, switches and bridges to facilitate the exchange of data among users using different sites. A site is a location that provides a starting point or gateway to other resources in the computer network. An example of a site is a web portal. A router located at a site can be referred to as a site router. The site router interacts with a master or central router such as a core router to make a request for data or exchange data with another site router. The core router can exchange data with more than one site router through various data links.
A data link is a communications transmission path or connection between two devices for exchanging data using a data link protocol that packetizes the data for transmission. Each data link may comprise one or more physical links that may be wireline and/or wireless links. A data link protocol is implemented at the data link layer (also commonly referred to as layer 2) of a network interconnect model, such as the well known Open Systems Interconnection (OSI) standard reference model. Examples of data link protocols include, but are not limited to: Point-to-Point protocol (PPP) as described by Internet Engineering Task Force (IETF) Request for Comments (RFC) 1661 to establish PPP data link connections between devices for data exchange over serial cable, phone lines, trunk lines, cellular telephones, specialized radio links, or fiber optic links; and a family of Frame Relay Forum (FRF) data link protocols for fast packet transmission (i.e., lacking error correction) between devices, an example of which is FRF.17 standard protocol.
In the event of a failure in the core router, the physical link of the core router becomes inactive, which may lead to a loss of data being communicated over the data links. To minimize data loss due to the failure of the core router, some networks use a redundancy mechanism that deploys a pair of core routers as active and inactive routers. When the computer network comprises a Wide Area Network (WAN), the router pair is sometimes referred to as Co-operative Wide area network Routers (CWRs). In the router pair, the active router is primarily responsible for data exchange with the various site routers. Further, the inactive router acts as a back-up router on stand-by to be used for data exchange when the active router fails. A relay switch is provided and coupled to each router pair. This relay switch is used to switch control to the inactive router when the active router fails, and vice versa. One advantage of the above redundancy mechanism is that the switching to the new active router usually occurs in well under three seconds and with minimum impact on traffic.
Further, the data exchange between the core and site routers in some networks needs to be secure. To facilitate secure communication in such networks, Security Associations (SAs) are established between the active core router and each of the site routers prior to data exchange. A SA is a relationship established between two network devices that defines security information (also referred to herein as security parameters) used to support secure communication between the two devices, wherein the security information may include, but is not limited to, encryption and authentication keys and algorithms, digital certificates, etc. However, establishing SAs in networks implementing the above-described redundancy mechanism can cause performance problems.
More particularly, in this type of network, only the active router maintains active data links with the site routers. Accordingly, SAs are established between the inactive router and each of the site routers only upon: loss of the data link between the previously active router and the site routers; switchover to the previously inactive router; and establishing active data links between the new active router and the site routers. This is due to certain protocols necessitating an active data link to establish the SAs. For example, the FRF.17 standard defines the use of Frame Relay privacy Protocol (FRPP) to establish the SAs, but FRPP security negotiations can be performed only when a directly connected layer two link is active. This is because FRPP uses an FRF.17 port for FRPP negotiations, and the sole FRF.17 port assigned to the router pair is only used by one of the core routers at a time. The resulting problem is that depending on the number of site routers involved, thereby, needing SAs established with the new core router, the switchover delay may exceed a few seconds and result in increased down time at the site routers.
Therefore, in a network that requires secure communications between an active router and various site routers, there exists a need for a mechanism that provides upon failure of the active router a resumption of the secure exchange of data between the inactive router and the site routers, which addresses at least some of the shortcomings in the prior art.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help improve understanding of various embodiments. In addition, the description and drawings do not necessarily require the order illustrated. Apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the various embodiments so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein. Thus, it will be appreciated that for simplicity and clarity of illustration, common and well-understood elements that are useful or necessary in a commercially feasible embodiment may not be depicted in order to facilitate a less obstructed view of these various embodiments.